Question about TableGen when adding LLVM Backend.

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1

Hello all,

I have some question about usage of TableGen when adding a new LLVM Backend. There are three place to use TableGen in basic steps of document “Writing an LLVM Compiler
Backend”:

  1. Describe the register set of the target. Use “TableGen” to generate code for register definition, register aliases, and register classes from a target-specific RegisterInfo.td input file.

  2. Describe the instruction set of the target. Use “TableGen” to generate code for target-specific instructions from target-specific versions of TargetInstrFormats.td andTargetInstrInfo.td.

  3. Describe the selection and conversion of the LLVM IR from a Directed Acyclic Graph (DAG) representation of instructions to native target-specific instructions. Use “TableGen” to generate code that matches patterns and selects instructions based on additional information in a target-specific version of TargetInstrInfo.td.

I have already read the document “TableGen Fundamentals” and write correspond .td files in each steps. However I don’t know which TableGen options should I use in 2, 3 or 4 steps as above. Would anyone mind to tell me??

thanks a lot

yi-hong

2

Look at Makefile.rules in the LLVM top-level directory. There is a bunch of targets executing $(TableGen).

You can also run 'make VERBOSE=1' to see the commands used to build the existing targets.

/jakob

3

Hello Jakob,

Is this means that TableGen execution is handled in Makefile. Porting programmer doesn’t need to execute TableGen by hand?

thanks

2011/3/10 Jakob Stoklund Olesen <stoklund@2pi.dk>

4

That's right.

You are going to be editing your .td files a lot, so you want that integrated in the build system.

5

In practice that'll mean adding the correct directives to CMakeLists.txt, not Makefile, right? That's what the targets I looked at did.
Or is that optional when you just invoke "make"?

Andreas

6

Hi Andreas,

In practice that'll mean adding the correct directives to
CMakeLists.txt, not Makefile, right? That's what the targets I looked
at did.

LLVM can be built using either CMake or the GNU Autotools. Your backend
ought to provide support for both build systems, so you should create a
CMakeLists.txt as well as a Makefile in your sub-directory.
The Makefile appears to be rather trivial because there's some automagic
going on - nevertheless, you will need one. :slight_smile:

Or is that optional when you just invoke "make"?

In that case you're using the Autotools, so your Makefile is going to be
utilized.

Best regards,
Christoph

7

Hi Christoph,

In practice that'll mean adding the correct directives to
CMakeLists.txt, not Makefile, right? That's what the targets I looked
at did.

LLVM can be built using either CMake or the GNU Autotools. Your backend
ought to provide support for both build systems, so you should create a
CMakeLists.txt as well as a Makefile in your sub-directory.

The Makefile appears to be rather trivial because there's some automagic
going on - nevertheless, you will need one. :slight_smile:

Now I see: My confusion came from seeing only the customized file names in BUILT_SOURCES. But Makefile.rules:1681 actually processes those files by *Gen*.inc.tmp name patterns.

Thanks for explaining,

Andreas

8

Those are part of two unrelated build systems - cmake and autoconf.

You need to maintain both for an in-tree target. Otherwise you only need build files for the build system you use.

/jakob